Primary cutaneous nocardiosis of the ankle caused by N. brasiliensis: a case report

Nocardia is a genus of aerobic, Gram-positive bacteria known for their �lamentous and branching morphology. N. brasiliensis is the most common species causing cutaneous nocardiosis. We present a 67-year-old woman who developed abscess-like lesions on the back of her right ankle after walking barefoot on soil. Cultures from the cutaneous lesions grew N. brasiliensis. Antibiotic therapy with trimethoprim-sulfamethoxazole given for a month provided near-complete resolution of her lesions.


Introduction
Nocardia is a genus of aerobic, Gram-positive bacteria known for their lamentous and branching morphology.Sharing characteristics of both bacteria and fungi, these actinomycetes are widely distributed in the environment, particularly in soil.Some species of Nocardia are opportunistic pathogens, capable of causing infections in humans, particularly those with compromised immune systems [1].The mechanism of virulence is either through inhalation or via entry portals of minor skin wounds and mucous membranes that render the body vulnerable to exposure to polluted soil or water in the environment.Nocardia infections often manifest as pulmonary or cutaneous diseases, posing challenges for diagnosis and treatment due to their variable clinical presentations.N. brasiliensis is the most common species causing cutaneous nocardiosis [1,2].

Case report
A 67-year-old woman with a 6-year history of type 2 diabetes mellitus presented with abscess-like lesions on the back of her right ankle.She reported walking barefoot on soil before the appearance of the lesions.One month before the current presentation, she sought treatment at another center, where she received one course each of oral fusidic acid followed by amoxicillin-clavulanate, without a response.At the current presentation, examination showed multiple abscesses on the back of her right ankle, measuring 1 x 2 cm in the greatest dimension (Fig. 1a).The abscesses were drained, specimens were collected for microbiologic examination, and empirical antibiotic therapy with ceftriaxone was initiated.Laboratory studies showed a white blood cell count of 11,400 cells/mm 3 (reference, 4,000-10,000), a C-reactive protein level of 19 mg/L (reference, < 5), and an erythrocyte sedimentation rate of 59 mm/h.After 10 days of empirical antibiotic therapy, the lesions partly remitted (Fig. 1b).Gram staining of the specimens showed leukocytes and Gram-positive lamentous bacteria (Fig. 2a).Cultures grew Nocardia brasiliensis (Fig. 2b, c), with discernible growth on the third day and prominent colonization on the fth day, characterized by R-type colonies with a uffy surface in chalky white color.
Identi cation of the pathogenic bacteria was further con rmed by the matrix-assisted laser desorption ionization-time of ight mass spectrometry (MALDI-TOF MS) system.Antimicrobial sensitivity testing was not performed due to the lack of Epsilometer test strips at the time of detection of the isolates.Based on the absence of speci c manifestations suggestive of other types of involvement, a diagnosis of primary cutaneous nocardiosis was made.Therapy was switched to trimethoprim-sulfamethoxazole two times daily in a combination dose of 160 mg of trimethoprim and 800 mg of sulfamethoxazole.Meanwhile, magnetic resonance imaging of the ankle showed no signs of osteomyelitis.At a 20-day follow-up visit, the patient's lesions had largely abated (Fig. 1c), and abnormal laboratory ndings had returned to normal, with no toxic effects associated with the antibiotic therapy.At a subsequent follow-up visit 10 days later, the cutaneous lesions had almost resolved (Fig. 1d) and the antibiotic therapy was discontinued.

Discussion
Primary cutaneous nocardiosis is a rare infection, most commonly caused by N. brasiliensis found in the environment, particularly in soil.It may manifest on a distal limb as super cial cellulitis or pyogenic abscess(es) that may further progress to sporotrichoid nodular lymphangitis characterized by spread along lymphatic channels or to a more destructive form, sinus tract formation [1,3,4].
Sulfonamides, in their most recent form of trimethoprim-sulfamethoxazole, have been shown to substantially improve primary cutaneous nocardiosis owing to their synergistic activity, making them the mainstay of therapy [1,5].As with the presented case, resolution of lesions has been reported with trimethoprim-sulfamethoxazole in several cases [3,6].
Teeming with diverse microorganisms, soil can harbor bacteria, fungi, and parasites that pose health threats upon contact with broken skin or through mucous membranes.Engaging in activities such as walking barefoot or gardening without protective gloves may expose individuals to the potential risk of contracting infections.In our case, the patient contracted the infection while walking barefoot on soil.In another report of sporotrichoid nodular lymphangitis from N. brasiliensis, the patient was infected through a thorn puncture in the hand while gardening [3].Therefore, adopting preventive measures, such as wearing shoes and gloves, becomes crucial in minimizing the chances of acquiring infections by soilborne pathogens while enjoying outdoor activities.

Figures
Figures

Figure 1 Primary
Figure 1